Field of the Invention
The invention relates to a method for controlling a fuel quantity to be fed to an internal combustion engine, in which a desired fuel quantity is determined on the basis of a desired operational performance of the internal combustion engine, a minimum air/fuel ratio at which soot-free operation of the internal combustion engine is possible is determined, a limiting value is determined for the maximum fuel quantity on the basis of the minimum air/fuel ratio and a measured air mass, and the fuel quantity to be fed is limited to that limiting value.
To date, the fuel quantity to be fed to an internal combustion engine has been determined on the basis of a desired operational performance of the internal combustion engine. In that case, a soot limit of a Diesel engine has been fixed by a map which is determined in a steady state and which could further be overlaid with a torque limiting map.
However, it has been found that such a procedure does not always permit optimum operation of the internal combustion engine. Sooting of the internal combustion engine has been found, particularly during acceleration.
An article entitled "Diesel-Einspritzung fur weniger Emissionen bei Nutzfahrzeugmotoren" ["Diesel Injection for Fewer Emissions in Commercial Vehicle Engines"], by Seher, MTZ, in Sonderheft (Special Issue) Motor und Umwelt 1992, page 31, discloses a method for determining the fuel quantity to be fed to an internal combustion engine within the framework of electronic Diesel injection in which a permissible fuel quantity for smoke limitation is determined by using maps. The map is a function of the rotational speed, charging pressure, induction-air temperature and fuel temperature. The smoke limitation is carried out over the entire operating range of the engine, with a distinction being drawn between steady and non-steady operation.
An article entitled "Die neuen Vierventil-Dieselmotoren von Mercedes-Benz" ["The New Four-Valve Diesel Engines from Mercedes-Benz"], by Horst Behnke, in MTZ, 54, 1993, page 490, discloses an electronic Diesel control and injection system in which the full-load injection quantity for smokeless engine operation is ensured by a limitation on the minimum permissible air/fuel ratio. In a smoke map which is provided for this purpose, an injection mass optimized by engine test stand tests is recorded while taking account of the atmospheric pressure, induction-air temperature and fuel temperature. Steady-state full-load smoke and smoke emissions during non-steady operation are thereby largely suppressed.